A spin-flip from a triplet to a singlet excited state, that is, reverse intersystem crossing (RISC), is an attractive route for improving light emission in organic light-emitting diodes, as shown by devices using thermally activated delayed fluorescence (TADF). However, device stability and efficiency roll-off remain challenging issues that originate from a slow RISC rate (kRISC). Here, we report a

Reverse intersystem crossing (RISC), originally considered forbidden in purely organic materials, has recently become possible by minimizing the energy gap between the lowest excited singlet state (S1) and lowest triplet state (T1) in thermally activated delayed fluorescence systems. However, direct spin-inversion from T1 to S1 is still inefficient when both states are of the same charge transfer (CT)

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Unidirectional and topological surface plasmon polaritons are currently attracting substantial interest and intense debate. Realistic material models and energy conservation considerations are essential to correctly understand extreme wave effects in non-reciprocal plasmonics, and to assess their potential for novel devices.

A correlation method that combines ultrasound and fluorescence enables imaging in strongly scattering environments.

A phase transition between disordered and quasi-ordered states, known as the Berezinskii–Kosterlitz–Thouless transition, has now been revealed in a two-dimensional photonic ‘fluid’. The interplay between phase singularities and coherence may lead to new vortex-based optical applications.

New methods to control how laser pulses propagate inside a plasma could signify the start of a global race to demonstrate truly high-energy compact particle accelerators.

The finding that hollow-core optical fibres can preserve the state of linearly polarized light over hundreds of metres with exceptional purity could benefit applications in sensing, gyroscopes and quantum optics.

Stripping heavy atoms in solid matter of most of their electrons requires the extreme conditions that exist in astrophysical plasmas, but are difficult to create in the laboratory1,2,3. Here we demonstrate solid-density gold plasmas with atoms stripped of up to 72 electrons (N-like Au72+) over large target depths. This record ionization is achieved by irradiating solid foils and near-solid-density

Recent technological advances in attosecond science hold the promise of tracking electronic processes at the shortest space and time scales. However, the necessary imaging methods combining attosecond temporal resolution with nanometre spatial resolution are currently lacking. Regular coherent diffractive imaging, based on the diffraction of quasi-monochromatic illumination by a sample, is inherently

Photochemical upconversion is a strategy for converting infrared light into more energetic, visible light, with potential applications ranging from biological imaging and drug delivery to photovoltaics and photocatalysis. Although systems have been developed for upconverting light from photon energies in the near-infrared, upconversion from below the silicon bandgap has been out of reach. Here, we

In addition to enhancing confinement, restricting optical systems to two dimensions gives rise to new photonic states, modified transport and distinct nonlinear effects. Here we explore these properties in combination and experimentally demonstrate a Berezinskii–Kosterlitz–Thouless phase transition in a nonlinear photonic lattice. In this topological transition, vortices are created in pairs and then

The availability of high-energy pulses with durations shorter than the period of their carrier frequency (sub-cycle) will reveal new regimes of strong-field light–matter interactions. Parametric waveform synthesis (that is, the coherent combination of carrier-envelope-phase-stable pulses that emerge from different optical parametric amplifiers) is a promising technology for the realization of tailored

Subluminal and superluminal light pulses have attracted considerable attention in recent decades1,2,3,4, opening perspectives in telecommunications, optical storage and fundamental physics5. Usually achieved in matter, superluminal propagation has also been demonstrated in vacuum with quasi-Bessel beams6,7 or spatio-temporal couplings8,9. Although, in the first case, the propagation was diffraction

Optical vortices, beams with spiral wavefronts and screw phase dislocations, have been attracting increasing interest in various fields. Here, we theoretically propose and experimentally realize an easy approach to generating optical vortices. We leverage the inherent momentum-space topological vortex-like response of polarization (strong polarization anisotropy) around bound states in the continuum

The development of high-performance near-infrared organic light-emitting diodes is hindered by strong non-radiative processes as governed by the energy gap law. Here, we show that exciton delocalization, which serves to decouple the exciton band from highly vibrational ladders in the S0 ground state, can bring substantial enhancements in the photoluminescence quantum yield of emitters, bypassing the

Using a photonic chip to generate the patterns of light needed for structured illumination microscopy could reduce the cost and complexity of super-resolution imaging.

Optical clocks held at slightly different heights provide a stringent test of general relativity comparable to space experiments and open new opportunities for clock-based geophysical sensing.

A particular class of focused, pulsed light beams can propagate self-similarly in free space at a fixed group velocity. Now, scientists present a law of refraction that determines how the group velocity of these beams changes as they refract at an interface between two materials.

By utilizing exciton resonances in atomically thick semiconductors, researchers have now demonstrated the ultimate downscaling of optical lenses and reported on their efficacious electrical tunability.

Refraction at the interface between two materials is fundamental to the interaction of light with photonic devices and to the propagation of light through the atmosphere at large1. Underpinning the traditional rules for the refraction of an optical field is the tacit presumption of the separability of its spatial and temporal degrees of freedom. We show here that endowing a pulsed beam with precise

Thermal noise is ubiquitous in microscopic systems and high-precision measurements. The control of thermal noise would reveal quantum regimes1 and enable fundamental physics searches2. Recently, nonlinearity in microresonators has enabled laser devices such as Kerr microresonator soliton frequency combs3. Soliton microcombs explore nonlinear dynamics and enable optical synthesizers4, optical clockwork5

In integrated photonics, specific wavelengths such as 1,550 nm are preferred due to low-loss transmission and the availability of optical gain in this spectral region. For chip-based photodetectors, two-dimensional materials bear scientifically and technologically relevant properties such as electrostatic tunability and strong light–matter interactions. However, no efficient photodetector in the telecommunication

Philip Warren Anderson is one of the founding fathers of modern condensed-matter physics. With his death on 29 March 2020, we have lost one of the most influential physicists of the twentieth century.

The contractility of cardiac cells is a key parameter that describes the biomechanical characteristics of the beating heart, but functional monitoring of three-dimensional cardiac tissue with single-cell resolution remains a major challenge. Here, we introduce microscopic whispering-gallery-mode lasers into cardiac cells to realize all-optical recording of transient cardiac contraction profiles with

Small-twist-angle (<2°) bilayer graphene has received extraordinary attention recently due to its exciting physical properties1,2,3,4,5,6,7,8,9,10,11. Compared with monolayer graphene, the Brillouin zone folding in twisted bilayer graphene (TBG) leads to the formation of a superlattice bandgap and substantial modification to the density of states4,6,7,12,13. However, these emerging properties have

III–nitride light-emitting diodes (LEDs) are the backbone of ubiquitous lighting and display applications. Imparting directional emission is an essential requirement for many LED implementations. Although optical packaging1, nanopatterning2,3 and surface roughening4 techniques can enhance LED extraction, directing the emitted light requires bulky optical components. Optical metasurfaces provide precise

Second-harmonic generation microscopy is a valuable label-free modality for imaging non-centrosymmetric structures and has important biomedical applications from live-cell imaging to cancer diagnosis. Conventional second-harmonic generation microscopy measures intensity signals that originate from tightly focused laser beams, preventing researchers from solving the scattering inverse problem for second-order

Research activities in the areas of X-ray imaging and ultraviolet sterilization illustrate how photonics is helping to combat the threat of COVID-19.

Asymmetric forward and backward transmission through photonic structures can be achieved via optical nonlinearities, but existing systems have typically used slow thermo-optic effects. A new resonator design has now enabled low-loss, non-reciprocal pulse routing based on the Kerr nonlinearity in integrated silicon waveguides.

Advanced computational imaging techniques have the potential to extract neural activity patterns from scattered data without reconstructing images.

A monolithic chip-scale ring laser gyroscope based on both Brillouin and Sagnac effects provides a sensitivity sufficient to measure sinusoidal rotations with an amplitude as small as 5 degrees per hour, thus enabling the first on-chip Earth rotation measurement.

Ultrashort pulse generation hinges on the careful management of dispersion. Traditionally, this has exclusively involved second-order dispersion, with higher-order dispersion treated as a nuisance to be minimized. Here, we show that this higher-order dispersion can be strategically leveraged to access an uncharted regime of ultrafast laser operation. In particular, our mode-locked laser—with an intracavity

The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Sensitive photodetectors that operate at a wavelength of 2 μm are required for applications in sensing and imaging but state-of-the-art devices are severely limited by high dark current density (Jdark). The narrow-bandgap materials required for mid-infrared (2–5 µm) detection are plagued by carrier recombination and band-to-band tunnelling; as a result, detectors must be operated at cryogenic temperatures

Fluorescence imaging is indispensable to biomedical research, and yet it remains challenging to image through dynamic scattering samples. Techniques that combine ultrasound and light as exemplified by ultrasound-assisted wavefront shaping have enabled fluorescence imaging through scattering media. However, the translation of these techniques into in vivo applications has been hindered by the lack of

High-performance interferometers, gyroscopes, frequency combs, quantum information experiments and optical clocks rely on the transmission of light beams with the highest possible spatial and polarization purity. Free-space propagation in vacuum unlocks the ultimate performance but becomes impractical at even modest length scales. Glass optical fibres offer a more pragmatic alternative, but degrade

Structured illumination microscopy (SIM) enables live-cell super-resolution imaging of subcellular structures at high speeds. At present, linear SIM uses free-space optics to illuminate the sample with the desired light patterns; however, such arrangements are prone to misalignment and add cost and complexity to the microscope. Here, we present an alternative photonic chip-based two-dimensional SIM

Exciton funnelling due to non-homogeneous strain was previously thought of as an efficient neutral exciton transport mechanism. New findings suggest that exciton funnelling might be negligible compared with another strain-dependent process, the conversion of neutral excitons into trions.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Using a photonic crystal slab combined with a conventional optical imaging system, a two-dimensional optical image differentiator is experimentally demonstrated for edge detection.

Delegates at the BiOS symposium heard how artificial intelligence can transform medical imaging, with its ability to improve quality, speed and molecular specificity.

Integrated quantum photonic chips offer the promise of a convenient, scalable platform for performing tasks such as quantum communication and information processing.

Dark-field microscopy is a widely used imaging method that emphasizes sharp edges and other small features, but typically requires specialized microscope components. Researchers have now engineered special substrates that enable dark-field microscopy using simple bright-field microscopes.

Orbital angular momentum (OAM) from lasers holds promise for compact, at-source solutions for applications ranging from imaging to communications. However, conjugate symmetry between circular spin and opposite helicity OAM states (±ℓ) from conventional spin–orbit approaches has meant that complete control of light’s angular momentum from lasers has remained elusive. Here, we report a metasurface-enhanced

The highly engineerable scattering properties of resonant optical antennas underpin the operation of metasurface-based flat optics. Thus far, the choice of antenna has been limited to shaped metallic and high-index semiconductor nanostructures that support geometrical plasmonic or Mie resonances. Whereas these resonant elements offer strong light–matter interaction and excellent control over the scattering

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.